Liquid processing apparatus and liquid processing method

ABSTRACT

In a liquid processing apparatus for forming a coating film on a polygonal substrate by spin coating in an ambient with a descending clean air flow, a spin chuck includes a support plate for substantially horizontally supporting the substrate thereon. Air flow control members are provided on the spin chuck such that the air flow control member being disposed adjacent to a periphery of the polygonal substrate supported on the spin chuck, wherein the air flow control member is not provided near corner portions of the substrate supported on the spin chuck. The liquid processing apparatus may includes an air flow regulation ring which is provided with an air inlet having an opening surrounding an outer periphery of the air flow control member, wherein the air inlet communicates with the exhaust unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional Application of, and claims the benefitof priority under 35 U.S.C. § 120 from, U.S. application Ser. No.10/796,179, filed Mar. 10, 2004, herein incorporated by reference, whichclaims the benefit of priority under 35 U.S.C. § 119 from JapanesePatent Application No. 2003-063852 filed Mar. 10, 2003.

FIELD OF THE INVENTION

The present invention relates to a liquid processing apparatus andmethod for use in a liquid process, e.g., a coating process forming aresist film, is performed by supplying a process liquid on a polygonalsubstrate such as a mask substrate (reticle) which is used upon anexposure process of photolithography.

BACKGROUND OF THE INVENTION

In a manufacture process of a semiconductor device or an LCD, a resistfilm forming process is photolithographically performed on a substrateto be processed. During such process, a mask substrate having apredetermined pattern lithographed thereon is employed in exposing thesubstrate to be processed. In order to lithographically form the maskpattern on the surface of the mask substrate, a series of steps aretaken: first, a resist is spin coated on the mask substrate made of,e.g., glass, to thereby form a resist film; and then the resist film isexposed and developed, to thereby obtain a desired pattern.

During the spin coating, the substrate G is rotated so that a helicalair flow pattern is generated on a surface of the substrate G, tothereby rapidly remove solvent (thinner) ambient from the surface of thesubstrate G, which in turn facilitates evaporation of the solvent fromthe coating solution. However, at a portion of the substrate G where arapid evaporation of the solvent takes place, the processing solutionfrom nearby gets attracted thereto by the surface tension thereof, andas a result, such portion of the substrate G tends to have a greaterthickness than that of other portions. In order to resolve such problem,it is desirable that the evaporation rate of the solvent on the surfaceof the substrate G is uniformly adjusted.

However, in a case of using a polygonal substrate G, as shown in FIG.1A, peripheral sides of the substrate G rotate cutting through an outerambient (ambient with low solvent concentration), which in turnfacilitates the evaporation taking place at such peripheral sides of thesubstrate G. As a result, not only a greatest thickness is obtained atthe corners of the substrate G, but also a thickness profile slantedtowards corners in one direction is obtained at the peripheral sidesthereof, as shown in FIG. 1B. These features greatly contribute to adeterioration of thickness profile of the substrate G.

Disclosed in Japanese Patent Laid-open Publication No. 2000-271524 is aspin chuck including a circular plate provided with a depressed portion,i.e., a square recess, in which a substrate is placed, to prevent theambient from coming into contact with the substrate, and in addition, amethod for controlling the air flow pattern upon rotation. Moreover,there is disclosed in Japanese Patent Laid-open Publication No.H8-131929 a method for controlling air flow for a non-polygonalsubstrate by installing a ring member around a peripheral portion of asemiconductor wafer.

In order to form a pattern with a uniform line width with respect to themask substrate, there is necessary to secure an in-surface uniformity ofa thin film resist layer. However, the conventional spin chuck cannotsufficiently suppress an increase in thickness at the corner portions ofthe polygonal substrate. An air flow that is produced at a surface ofthe substrate G during a rotation thereof is considered as acontributing factor in such feature. Accordingly, there is a need toexamine a way to adequately control the air flow that occurs at thesubstrate G.

In addition, with a conventional spin chuck 100, a loading/unloadingprocess of a substrate G is somewhat complicated. Namely, when placingthe substrate G onto the spin chuck 100, a substrate G that is carriedin by, e.g., a transfer arm, is placed on, e.g., elevating pinsprotruded through a recess (a depressed portion) 101, and then thetransfer arm is retracted and the elevating pins are lowered, to loadthe substrate G in the recess 101. In such a loading/unloading process,direct loading of the substrate G into the recess 101 is difficult toachieve, and thus such process of loading and unloading the substrate Gmay become cumbersome. Furthermore, the time required in completing theseries of such processes may deteriorate throughput.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a liquidprocessing apparatus and method capable of ensuring a uniform thicknessof a coated film.

It is another object of the present invention to provide a liquidprocessing apparatus wherein a loading/unloading of a substrate caneasily be carried out.

In accordance with an aspect of the present invention, there is provideda liquid processing apparatus for forming a coating film on a polygonalsubstrate by spin coating in an ambient with a descending clean airflow, including: a spin chuck including a support plate forsubstantially horizontally supporting the substrate thereon, the spinchuck rotating the substrate in a substantially horizontal plane; a cupdisposed around the substrate supported on the spin chuck; an exhaustunit for evacuating an inside of the cup; a supply nozzle for supplyinga coating solution to a top surface of the substrate supported on thespin chuck; and at least one air flow control member provided on thespin chuck, the air flow control member being disposed adjacent to aperiphery of the polygonal substrate supported on the spin chuck,wherein the air flow control member is not provided near corner portionsof the substrate supported on the spin chuck.

The liquid processing apparatus may further include an air flowregulation ring including an air inlet having an opening surrounding anouter periphery of the air flow control member, wherein the air inletcommunicates with the exhaust unit.

With the above-described apparatus of the present invention, in case ofdrying coating solution on the substrate by rotating the substrate, ahelical air flow including evaporative substance flowing from a centerportion to a periphery of the substrate along the surface thereof isproduced. The helical air flow continuously flows through the topsurfaces of corner portions of the substrate. Accordingly, an incrementin the film thickness at the corner portions of the substrate issuppressed and, in terms of thickness profile, high in-surfaceuniformity can be achieved.

In accordance with another aspect of the present invention, there isprovided including: a liquid processing method for forming a coatingfilm on a polygonal substrate by spin coating in an ambient with adescending clean air flow, comprising the steps of: (a) supporting thepolygonal substrate by a spin chuck and placing at least one air flowcontrol member, which rotates with the spin chuck, along a peripheryportion of the substrate except at corner portions thereof; (b)supplying a top surface of the substrate supported on the spin chuckwith coating solution and centrifugally spreading the coating solutionby rotating the spin chuck about a normal axle; (c) removing a part ofthe coating solution on the top surface of the substrate by rotating thesubstrate at a first rotating speed; and (d) evaporating solventincluded in the remaining coating solution on the top surface of thesubstrate by rotating the substrate at a second rotating speed slowerthan the first rotating speed.

In accordance with further another aspect of the present invention,there is provided including: a liquid processing method for forming acoating film on a polygonal substrate by spin coating in an ambient witha descending clean air flow, comprising the steps of: (a) supporting thepolygonal substrate by a spin chuck and placing at least one air flowcontrol member, which rotates with the spin chuck, along a peripheralportion of the substrate except at corner portions thereof; (b)supplying a top surface of the substrate supported on the spin chuckwith coating solution and centrifugally spreading the coating solutionby rotating the spin chuck about a normal axle; (c) removing a part ofthe coating solution on the top surface of the substrate by rotating thesubstrate at a first rotating speed, after stopping the supplying of thecoating solution is stopped; and (d) evaporating solvent included in theremaining coating solution on the top surface of the substrate, byrotating the substrate at a second rotating speed slower than the firstrotating speed, wherein, at least in the step (d), in addition to an airflow produced by the rotation of the spin chuck, a horizontally outwardair flow is produced from a periphery of the air flow control member.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of preferred embodiments,given in conjunction with the accompanying drawings, in which:

FIG. 1A is a schematic top view showing a case of a resist spin coatingon a polygonal substrate by using a conventional apparatus;

FIG. 1B shows a thickness distribution of the resist film formed on thepolygonal substrate by the conventional spin coating process;

FIG. 2 illustrates a sectional view of a liquid processing apparatus inaccordance with a first preferred embodiment of the present invention;

FIG. 3A describes a top view of a spin chuck;

FIG. 3B sets forth a partial enlarged view showing a polygonal substratesupported by the spin chuck;

FIG. 4 depicts a perspective view of the spin chuck;

FIG. 5 provides a schematic top view of a transfer arm supporting thesubstrate;

FIGS. 6A and 6B present a top view and a partial sectional view of thesubstrate, respectively;

FIGS. 7A and 7B represent an enlarged side view and an enlarged top viewshowing the substrate supported by supports of the transfer arm,respectively;

FIGS. 8A to 8C offer perspective views for illustrating a process ofloading the substrate to the spin chuck from the transfer arm;

FIG. 9 is a schematic top view illustrating an air flow pattern producedon a top surface of the substrate upon spin drying;

FIG. 10A shows an exploded perspective view of a spin chuck inaccordance with another embodiment;

FIG. 10B depicts a partial enlarged section view of the spin chuck inFIG. 10A;

FIG. 11A provides an exploded perspective view of a spin chuck inaccordance with further another embodiment;

FIG. 11B sets forth a cross sectional view of the spin chuck in FIG.11A;

FIG. 12 presents a top view of a spin chuck in accordance with stillfurther another embodiment;

FIG. 13 represents a top view of an air flow control member (hole type)in accordance with still further another embodiment;

FIG. 14 describes a liquid processing apparatus in accordance with asecond preferred embodiment of the present invention;

FIG. 15 depicts a schematic top view of a coating/developing apparatusincluding the liquid processing apparatus of the present invention;

FIG. 16 offers a schematic perspective view of the coating/developingapparatus including the liquid processing apparatus of the presentinvention;

FIG. 17 is a graph three-dimensionally showing a thickness distributionof a resist film formed on the substrate by using a method of thepresent invention;

FIG. 18 provides a graph three-dimensionally showing a thicknessdistribution of a resist film formed on a substrate by using a method ofthe present invention; and

FIG. 19 is a graph three-dimensionally showing a thickness distributionof a resist film formed on a substrate by using a conventional method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings.

First Embodiment

As shown in FIG. 2, a spin chuck 2 is accommodated in a cup 3 of acoating process apparatus 1. The spin chuck 2 receives a mask substrateG as a substrate to be processed from a transfer arm 5 (shown in FIGS. 5and 8A to 8C) and a predetermined coating process is executed on thesubstrate G. The substrate G includes a chromium oxide (Cr₂O₃) coatingfilm formed on a square quartz plate having a side (L1) of 152±0.4 mmand a resist layer formed thereon, wherein a plate thickness of thesubstrate G is ¼ inch (6.35±0.1 mm), and a projection length of a C face(13 c in FIG. 7A) ranges from 0.2 to 0.6 mm.

The spin chuck 2 is provided with a support plate 23 and air flowcontrol members 26. The support plate 23 includes upright walls 24 and aplurality of spacers 28 to secure the polygonal substrate G; and isconnected with a driving member 22 via a rotation axle 21. The drivingmember 22 is controlled by a controller 80. The driving member 22 iscapable of rotating the spin chuck 2 about the Z-axis and verticallymoving the spin chuck 2 along the Z-axis.

As shown in FIGS. 3A and 10A, there are provided on a top surface of thesupport plate 23 a number of protrusions (substrate support member) 27such that they are located near center portions of sides of thesubstrate G. The protrusions 27 are provided to prevent foreignsubstances from clinging to a bottom surface of the substrate G, bysupporting the bottom surface of the substrate G slightly above a topsurface of the support plate 23, as shown in FIG. 10B. Moreover, pluralnozzles (not shown) for rinsing a bottom surface of the substrate G isinstalled at the bottom of support plate 23, such that rinse solutioncan be ejected from the nozzles through the support plate 23 to cleansethe bottom surface of the substrate G.

In addition, there are provided on the top surface of the support plate23 a pair of spacers 28 at each corner portion thereof, as shown inFIGS. 3A, 3B and 10A. The spacers 28 serve to align the substrate G withthe spin chuck 2 and to place the substrate G spaced apart from theupright walls 24 of the spin chuck 2, as shown in FIGS. 3B, 4, and 10B.In other words, due to the spacers 28, the lateral sides 13 e (FIG. 7A)of the substrate G do not come in planar contact with the upright walls24 of the spin chuck.

Furthermore, portions of protrusions 27 and spacers 28 coming in directcontact with the substrate G are coated with polyetheretherketone(PEEK)to prevent scrapes or scratches from occurring on the substrate G. PEEKmay include carbon fiber. Additionally, e.g., aluminum, an aluminumalloy, a stainless steel coated with fluororesin, PEEK, or a combinationthereof can be employed for other portions of spin chuck in order toprevent generation of foreign substances.

As shown in FIG. 2, there is provided a cup 3 of a first preferredembodiment of the present invention, the cup 3 including an inner cup 31and an outer cup 30 to surround periphery of the spin chuck 2. The innercup 31 has a cylindrical lower portion and a truncated upper portioninclined inwardly and upwardly from the lower portion such that openingat a top end of the inner cup 31 is less than that at a bottom endportion thereof. The outer cup 30 is vertically movably supported by anelevating mechanism (not shown). When the outer cup 30 is elevated bythe elevating mechanism, the inner cup 31 is interlocked with the outercup 30 at a portion of movement stroke of the outer cup 30 and iselevated therewith.

Installed below the spin chuck 2 is a circular plate 32. A centerportion of the circular plate 32 is penetrated by the rotation axle 21of the spin chuck. A seal (not shown) is employed to fluid-tightly seala gap between the rotation axle 21 and the circular plate 32. Aperipheral portion of the circular plate 32 has a downward slope,directly under which there are provided a concave portion 39 a and aconvex portion 39 b along the entire circumference thereof, and therebyforming a labyrinth shaped winding fluid channel at a bottom portion ofthe cup 3.

At a bottom portion of the convex portion 39 b there are provided aplural number of exhaust paths 33, which communicate with a suction sideof a vacuum pump of an exhaust unit 81. In order to uniformly evacuatethe interior of the cup 3, the exhaust paths 33 are arranged at thebottom portion of the convex portion 39 b at regular intervals.

Moreover, provided outside the concave portion 39 a placed at the bottomsurface of the cup is a fluid receptacle 35 with a partition wall 34disposed therebetween. A bottom surface of the fluid receptacle 35 isoutwardly slanted a little and an opening for a liquid drain path 36 isprovided at the lowest region of the slanted bottom surface, the liquiddrain path 36 communicating with a drain unit 82. Although a singleliquid drain path 36 is installed in the present embodiment, two or moreliquid drain paths 36 may be provided.

At the labyrinth shaped bottom portion of the cup 3, the drainage fluid,i.e., resist solution and rinsing solution, is separated into liquid andgas. Thus separated gas is discharged to the exhaust unit 81 via theexhaust path 33, whereas the separated liquid is sent to the drain unit82 via the liquid drain path 36. The operation of the exhaust unit 81and the drain unit 82 is controlled by the controller 80.

The cup of the present embodiment has a discharging volume of, e.g., 900inch aqua (260 to 270 Pa), which is about five to six times that of acup of a silicon wafer coating apparatus. With the present coatingapparatus, by making the discharging volume of the cup significantlygreater than that of the silicon wafer coating apparatus, even a minuteamount of foreign substances is prevented from adhering to the substrateG inside the cup 3.

A ring plate 37 is provided above the cup 3. The ring plate 37 has aninner diameter smaller than the opening of the cup 3, e.g., 100 to 160mm and an outer diameter greater than the opening of the cup 3. The ringplate 37 is vertically movably supported by a Z-drive mechanism 85.

By shifting the ring plate 37 with the Z-drive mechanism 85 controlledby the controller 80, the distance H1 between a top surface of the airflow control member 26 (or the substrate G on the spin chuck) and abottom surface of the ring plate 37 is controlled. The distance H1 is asignificant parameter along with a flow rate and a velocity of adescending clean air flow, a cup discharging volume, an area of thesubstrate G, an area and a shape of the air flow control members, anopening area of ventilation holes 25, etc., which influences auniformity in thickness of a coated resist layer. In the presentembodiment, the distance H1 was set as 20 mm. The distance H1 ispreferably in a range from about 15 to 40 mm, more preferably in a rangefrom about 20 to 30 mm, and most preferably about 20±1 mm. Anexcessively large distance H1 reduces the effect of controlling thedescending clean air flow. On the other hand, an excessively smalldistance H1 leads to a disparity in the thickness of the resist layer(deterioration of film thickness uniformity) at a boundary between anarea where the descending clean air stream is ejected to and an areawhere not.

A supply nozzle 4 is provided at a position facing a top surface 13 a(FIG. 7A) of the substrate G mounted on the spin chuck 2, for supplyinga processing solution, e.g., coating solution such as resist solution,onto the surface of the substrate G. The supply nozzle 4 is movable notonly vertically but also forwards and backwards.

Hereinafter, the spin chuck 2 will be described in detail with referenceto FIGS. 3A, 3B, and 4.

A substrate mounting portion of the spin chuck 2 is a plate 23 of asubstantially polygonal shape slightly greater than the substrate G. Theupright wall 24 is formed at each side of the plate along the peripherythereof. That is, the plate 23 and the upright walls 24 form a recessedportion in which the substrate G is placed. In addition, at positions onthe plate 23 corresponding to the respective corner portions of asubstrate G mounted thereon, there are provided cutout portions 25 eachhaving, e.g., an arc shape. Specifically, at a state wherein thesubstrate G is mounted on the plate 23, the corner portions of the plate23 are cut out by, e.g., 7 mm. The cutout portion 25 is preferably in arange from about 4 to 10 mm, more preferably in a range from about 5 to9 mm, and even more preferably in a range from about 6 to 8 mm. However,the most preferable size of the cutout portion 25 is about 7 mm. If thesize of the cutout portion 25 falls below 4 mm, e.g., 3 mm, a thicknessof the resist layer in the corner portions becomes greater than that ofother portions, as shown in FIG. 1B. Similarly, when the size of thecutout portion 25 exceeds 10 mm, there is a disparity in the thicknessof the resist layer in the corner portions.

Provided on a top edge of each of the four upright walls 24 is a wingshaped air flow control member 26, outer rim of which has a shape of anarc. Top surfaces of the air flow control members 26 are generally flushwith the top surface. of the substrate G and extend outwardly in theXY-plane. The air flow control members 26 surround all four sides of thesubstrate G, excepting the corner portions thereof. That is, the airflow control members 26 are substantially at the same level as the topsurface of the substrate G or may be positioned lower at maximum of 0.5mm than the latter. The air flow control members 26 are not provided atthe corner portions of the substrate G. Furthermore, the top surface ofthe air flow control members 26 are preferably subjected to surfacetreatment by, e.g., fluorine coating or Tufram treatment for waterrepellence, in order to enhance the removal (pealing-off) of the resistsolution therefrom.

Furthermore, on the top surface of the plate 23, a protrusion 27 isprovided at a position corresponding to, e.g., about a center portion ofeach side of the substrate G, to support the substrate G slightly abovethe top surface of the plate 23, to thereby prevent foreign substancesfrom being attached to the bottom surface of the substrate G.

The gap between peripheral sides of the substrate G mounted on the plate23 and the upright walls 24 is about 1.5+0.2 mm. In the gap, there areprovided a plurality of spacers 28 to horizontally support lateral sidesof the corner portions of the substrate G, thereby preventing thesubstrate G from moving when the spin chuck 2 is rotated. The spacers 28further serve to align the substrate G to a desired position on the spinchuck 2 for the substrate G to be securely maintained thereat. Moreover,portions of protrusions 27 and the spacers 28 coming into contact withthe substrate G are coated with, e.g., resin such as PEEK, to therebyprotect the substrate G from scratches or scrapes, wherein PEEK mayinclude carbon fiber.

The plate 23 can be a circular plate having a recess on a top surfacethereof. Further, a cutout portion 25B (see FIG. 12) may be provided ata position on the plate 23B corresponding to each corner portion of thesubstrate G. Moreover, ventilation holes 25C (see FIG. 13) may beprovided at positions on the plate 23 corresponding to the cornerportions of the substrate G, respectively.

Hereinafter, a transfer arm 5 and the mask substrate G will be describedin detail with reference to FIGS. 5, 6A, 6B, 7A, 7B, 8A, 8B, and 8C.

The transfer arm 5 includes a horizontal arm member 51 driven by aXYZB-driving mechanism (not shown), for loading/unloading the masksubstrate G to/from a spin chuck. The horizontal arm member 51 includesa ring shaped main body having a cutout leading end and four supportextrusions 52. The four support extrusions 52 are inwardly protrudedfrom an inner periphery of the ring shaped main body and support a Cface 13C of each corner portion of the mask substrate G.

A bottom surface 13 b and side surfaces 13 e of the mask substrate G areprohibited from being in contact with other objects, to preventcontamination by clinging of foreign substances thereto. Areas 11 of themask substrate G which are allowed for contact with other objects arelimited to only four corner portions and four center portions of thesides as shown in FIG. 6A. Moreover, the support extrusions 52 of thearm member are configured to come into contact only with C faces 13 c ofthe mask substrate G, and substantially not with the bottom surface 13 band the side surfaces 13 e of the substrate G, as shown in FIG. 7A.Specifically, each support extrusion 52 includes a tapered guide surface52 a, a leading end stopper portion 52 b, and an inflection portion 52c. When the substrate G is received by the transfer arm 5, the substrateG slides along the tapered guide surfaces 52 a in a state that only theC faces 13 c are in contact therewith, and stops as the C faces 13 creach the inflection portions 52 c. A diameter of the inscribed circleof the leading end stopper portions 52 b is set to be smaller than thatof the circumscribed circle of the mask substrate G, and thus there isno concern for the mask substrate G to be dislodged out of the supportextrusions 52. From a plane view, as shown in FIG. 7B, a pair of leftand right halves of the inflection portion 52C of each support extrusion52 contacts the mask substrate G at a corner portion thereof.

The substrate G, as shown in FIG. 6B, includes a transparent member 12 asuch as quartz having thereon a chromium oxide (Cr₂O₃) coating film 12Bon top of which there is a resist coating layer 12C. An averagethickness of the chromium oxide (Cr₂O₃) coating film 12B ranges fromabout 30 to 60 nm, and that of the resist coating film 12C ranges fromabout 400 to 800 nm. Moreover, a length LI of each side of the masksubstrate G is about 152±0.4 mm; a thickness of the substrate G is about¼ inch (6.35±0.1 mm); and each of a horizontal and a normal projectionlength of each C face 13 c ranges from about 0.2 to 0.6 mm.

Hereinafter, an example for a method of loading and unloading thesubstrate G by using the transfer arm 5 will be described in short.

First, as illustrated in FIG. 8A, the transfer arm 5 carrying thesubstrate G is horizontally moved to a region above the spin chuck 2.The spin chuck 2 is rotated to align the cutout portions 25 with thecorner portions of the substrate G mounted on the transfer arm 5.

Next, as illustrated in FIG. 8B, while the substrate G is mounted on thetransfer arm 5, the transfer arm 5 is lowered such that an area that issurrounded by the arm member 51 meets the spin chuck 2. As thehorizontal arm member 51 carrying thereon the substrate G passes aroundthe plate 23 of the spin chuck 2, the substrate G is loaded onto thespin chuck 2. At this time, the substrate G is aligned to apredetermined position by the spacers 28 and the bottom surface thereofis supported by the protrusions 27 so that the substrate G is held onthe spin chuck 2. Thereafter, as illustrated in FIG. 8C, when thetransfer arm 5 reaches a region below the plate 23, the transfer arm 5horizontally moves backward passing around the rotation axle 21. Whenunloading the substrate G from the spin chuck 2 by the transfer arm 5,the above-mentioned process can be performed in a reverse order.Although, in this example, the transfer arm 5 is vertically movableduring the operation, the spin chuck 2 may be configured to bevertically movable in lieu thereof or both of them may be made to movevertically relative to each other.

Hereinafter, a method for executing a predetermined liquid processing,e.g., forming a coating layer on a surface of a substrate G, by usingthe above-mentioned apparatus, will be described in detail.

First, the inner cup 31 and the outer cup 30 are both set at loweredpositions and the ring plate 37 is set at an elevated position. Then,the spin chuck 2 is raised up to above the outer cup 30, and byemploying the above-mentioned process, the substrate G is transferredfrom the transfer arm 5 to the spin chuck 2. Subsequently, the inner cup31 and the outer cup 30 are set at elevated positions, and the ringplate 37 is set above the outer cup 30. Next, a supply nozzle 4 isguided to a position facing a center portion of the substrate G by usinga XYZ-drive mechanism 84. While the spin chuck 2 is rotated at a firstrotational speed of, e.g., 2500 rpm, for duration of, e.g., 2 to 3seconds to thereby rotates the substrate G at a high speed, a processingsolution of resist solution is discharged toward the center of thesubstrate G for, e.g., 1.5 seconds, from the supply nozzle 4 through aresist solution supply unit 83. Due to a centrifugal force, the resistsolution that has reached the substrate G spreads out to a peripherythereof, and a surplus of the resist solution on the substrate G isremoved.

Thereafter, while the supply nozzle 4 is retracted; and, at the sametime, the substrate G is rotated at a second rotational speed of a lowrotational speed of, e.g., 1000 rpm, for, e.g., 15 to 30 seconds, tothereby facilitate the evaporation of the thinner contained in theresist solution spread on the surface of the substrate G. The remainingresist solution forms a resist film having a thickness of, e.g., 0.6.mu.m (600 nm), on the surface of the substrate G. Finally, the innercup 31 and the outer cup 30 are set at the lowered positions; and thespin chuck 2 is raised to transfer the substrate G to the transfer arm 5for the unloading thereof.

During such spin coating, the surplus resist solution is removed by thehigh speed rotation and dried by the low speed rotation. In the highspeed rotation process, resist solution flows in radial directions ofthe substrate G and is removed.

On the other hand, in the low speed rotation process, a descending airflow collides with the resist coating film, and the drying actionthereof, solvent is eliminated from the resist coating layer. As aresult, the resist coating layer is solidified. During the drysolidifying process, the resist solution on the coating layer slightlyflows to the periphery, which affects the thickness profile of thecoating layer. Since a surplus of the resist solution is eliminated inthe previous high speed rotation process and as a result the resistsolution on the substrate G forms a thin film thereon, the low speedrotation merely serves a purpose of drying, and thus the inventors ofthe present invention believe that a descending air flow entering thecup 3 via the ring plate 37 and flowing on the surface of the substrateG from the center to the periphery thereof is what affects the thicknessprofile rather than the centrifugal force produced during rotation.Although it is clear from an example to be described later that thecoating profile is improved by employing the spin coating methoddescribed above, the air flow forming mechanism at the surface of therotating substrate G during the drying process is not experimentallyascertained; and the inventors of the present invention assume theformation of such air flow pattern as follows.

As schematically shown in FIG. 9, when the substrate G is rotatedclockwise at a low speed, an apparent air flow that appears to flowcounterclockwise relative to the substrate G is produced on the surfaceof the substrate G. The air containing solvent helically flows along thesurface of the substrate G from the center portion toward a peripherythereof. At the periphery of the substrate G, the air flowing outsidethe substrate G travels along the top surfaces of the air flow controlmembers 26 and returns back to the substrate G. Accordingly, as shown inthe drawing, a helical air flow is produced from the center portion ofthe substrate G to the periphery (corner portions) thereof. As a result,an air flow containing high concentration of solvent reaches even thecorner portions of the substrate G. Such air flow changes its directionat places where the air flow control members 26 are not provided andthen flows outwardly through (passing through upper parts of) the cornerportion of the substrate G in a diagonal direction. Since an aircontaining high concentration of solvent continuously passes through theupper parts of the corner portions of the substrate G in the diagonaldirections thereof, an evaporation of the solvent is suppressed at thecorner portions of the substrate G. As a result, the drying rate of thecoating film at the corner portions becomes substantially the same asthat of other portions, improving uniformity in the thickness of thecoating film on the substrate G.

Although in the present embodiment, the resist solution is suppliedwhile rotating the substrate G at the first rotational speed, the resistsolution can be supplied, e.g., while the substrate G is at rest, andthen the substrate G may be rotated. In this case, spreading anddry-solidifying the resist solution on the surface of the substrate G isperformed by a single process.

The above-mentioned embodiment employs an arrangement including a spinchuck 2 that has air flow control members 26 surrounding the peripheryof the substrate G with the exception of the corner portions. Therefore,a helical air flow containing high concentration of solvent and flowingalong the surface of the substrate G continuously passes through theupper parts of the corner portions. As a result, the evaporation of thesolvent is suppressed at the corner portions of the substrate G and,consequently, an in-surface evaporation of the solvent becomes uniformso that an in-surface uniformity even throughout the periphery of thesubstrate G is obtained. In other words, it is possible to obtain a highprecision thickness profile on the surface of the substrate G so that amask pattern having a uniform line-width can be obtained.

Moreover, in the above-described embodiment, the cutout portions 25 areprovided on the spin chuck 2, so that loading and unloading of thesubstrate G into and from the recessed portion in the spin chuck 2 isfacilitated by utilizing the corner portions of the substrate Gprotruding through cutout portions 25 when transferring the substrate Gbetween the transfer arm 5 and the spin chuck 2. As a result, especiallyeven in a case of repeatedly processing the substrates G, thedeterioration of throughput can be suppressed.

In addition, in the above-described embodiment, by installing the ringplate 37 in such a configuration that an air flow is directed toward aposition corresponding to the center portion of the substrate G, the airflow entering the cup 3 flows toward a center portion of the substrate Gand then is directed outwardly along the surface of the substrate G inparallel thereto; and, as the air flow speed is increased, a formationof turbulent flow at the corner portions of the substrate G can besuppressed. Resultantly, effects of the air flow at the corner portionsof the substrate G can be suppressed, thereby resulting in a highprecision in-surface thickness profile of the coating film on thesubstrate G.

Furthermore, in the above-described embodiment, by not providing the airflow control members 26 at the corner portions of the substrate G, evenwhen a resist solution spreads to the gaps between the substrate G andthe upright walls 24 during the coating process for example, thesolution can be discharged therethrough, thereby preventing acontamination of the bottom surface and the side surfaces of thesubstrate G. Moreover, such arrangement suppresses attraction of theresist solution spread into the gaps towards the peripheral edges of thesubstrate G by surface tension thereof during the drying process,thereby suppressing a deterioration of thickness profile.

In case the entire peripheral portions of the substrate G are surroundedby the air flow control members 26, the solution should be removedpassing through the air flow control members 26. In this case, there mayexist a disparity in the removality of the solution due to, e.g.,factors such as surface roughness. However, by not providing the airflow control members 26 at the cutout portions 25 as in theabove-described embodiment, such portions can be used in continuouslyremoving the resist solution. As a result, such arrangement offers anadvantage of providing a film of solution with a thin film profile of anadequate thickness on the surface of the substrate G.

Moreover, the present invention is not limited to the arrangementwherein the upright walls 24 are provided along the sides of thepolygonal support plate 23. As illustrated in FIG. 10A, there may beprovided a generally circular plate 23′ having a center portion formounting thereon a substrate, cutout portions 25, and air flow controlmembers 26′ each being provided through a protruding spacer 29. In otherwords, such arrangement provides a gap between the plate 23′ and eachair flow control member 26′. In such a case, as illustrate in FIG. 10B,it is preferable that an inner end portion of each air flow controlmember 26′ facing the substrate G is of a slanted surface having adownward and outward slant, and the top surface of the substrate G isplaced between a top and a bottom end of the inner end portion of theair flow control member 26′. For example, it is preferable that the topsurface of the substrate G is located at a level lower than that of theair flow control member 26′ (the top of the inner end portion), forexample by 0.5 to 1 mm. Under such configuration, the air flow formed onthe surface of the substrate G can be regulated and the same results canbe achieved as in the above-described case.

Moreover, in such a case, during, e.g., a high speed rotation process,the resist solution removed from the surface of the substrate G isdischarged through the gaps provided between the air flow controlmembers 26′ and the plate 23′. Accordingly, there are less chances ofthe resist solution flowing back to the bottom surface of the substrateG and therefore contaminating of the bottom surface of the substrate Gand the surfaces of the plate 23′ and the protrusion 27 can besuppressed. Further, in comparison with the above-described arrangement,the removability of the resist solution improves in the present caseand, therefore, a film solution with an appropriate thin film profilecan be formed on the surface of the substrate G.

Hereinafter, a modification of the first embodiment will be described indetail with reference to FIGS. 11A, 11B, 12, 13, and 14.

In the spin coating process, an air flow formed on the surface of thesubstrate G by rotating the substrate G during the drying phase affectsthe thickness profile, as described above. Further, in case a differentconfiguration of a cup 3 is used, a different air flow pattern isproduced on the surface of the substrate G even though an identical spinchuck 2 is used, which affects the thickness profile. In the presentembodiment, based on the fact that a combination of the cup 3 and thespin chuck 2 may cause a synergy effect, the combination of the two isappropriately selected in order to improve the thickness profile.

There is shown in FIG. 11A a spin chuck 2A including a circular plate23″ for mounting thereon a substrate G, on top of which there isprovided via spacers 29 an air flow control member 26″ of a circularplate (flat plane) having an opening greater than the substrate G. Thespin chuck 2A of the present modified embodiment corresponds to the spinchuck 2 shown in FIG. 10A where the end portions of neighboring air flowcontrol members 26 are connected each other at portions corresponding tothe cutout portions 25.

A spin chuck 2B in FIG. 12 includes a substantially square support plate23B at a bottom portion thereof. Peripheral flanges of the support plate23B are secured to a periphery of an opening of an air flow controlmember 26B by using screws. Since the opening of the air flow controlmember 26B is of a square shape and corner portions of the substantiallysquare support plate 23B are cutout, as viewed from above, there areformed ventilation holes 25B at positions corresponding to the cornerportions of the substrate G, respectively. The shape and size of theventilation holes 25B are determined by a combination of the opening ofthe air flow control member 26B and the cutout corner portions of thesupport plate 23B. In the present embodiment, each ventilation hole 25Bhas a radius ranging from about 5 to 10 mm having a shape of a quarterof a circle.

At the periphery of the opening in the air flow control member 26B,there are provided a plural number of spacers 28 to secure the substrateG on the spin chuck 2B.

A spin chuck 2C shown in FIG. 13 includes a support plate 23C havingventilation holes 25C formed therein instead of the cutout portions. Theventilation holes 25C provide independent openings at four cornerportions of the support plate 23C, respectively. That is, theventilation holes 25C are spaced apart from the periphery of the supportplate 23C. In the present embodiment, each ventilation hole 25C has aradius ranging from about 5 to 10 mm in a shape of a quarter of acircle.

Second Embodiment

Hereinafter, a second embodiment of the present invention will bedescribed with reference to FIG. 14. The description of parts that aresimilar to those in the first embodiment will be omitted.

A cup 6 employed in the second embodiment includes an air flowregulation ring 61 which is placed around an outer periphery of one ormore air flow control members 26D of the spin chuck 2D, whilemaintaining a gap of, e.g., 2 mm therebetween. A flat top surface of theair flow regulation ring 61 is substantially parallel to the top surfaceof the air flow control members 26D. The air flow regulation ring 61further includes bottom surface, the bottom surface having a flat innerportion and an outer portion slanted downwardly toward outside. Further,the top surface of the air flow regulation ring 61 is placed at a levelslightly, e.g., 1 mm, higher than those of the air flow control members26D. By surrounding the outer peripheries of the air flow control member26D, the air flow regulation ring 61 forms an air inlet 61 a.

Furthermore, there is provided a circular plate 62 around the rotationaxle 21 under the air flow regulation ring 61. A ring member 63 having agenerally triangular cross section is provided to surround a peripheryof the circular plate 62.

Moreover, through-holes 64 are provided at a top surface of a supportplate 23D, through which elevating pins 65 are vertically movablyinstalled to support and elevate the substrate G from bellow,respectively. The elevating pins 65 cooperate with, e.g., the transferarm 5 to enable loading and unloading of the substrate G.

The drainage fluid (resist solution and rinsing solution) is separatedinto gas and liquid at a labyrinth shaped bottom portion of the cup 6.Thus separated gas is discharged to the exhaust unit 81 via the gasexhaust path 33, whereas the separated liquid is sent to the drain unit82 via the liquid drain path 36. The operation of the exhaust unit 81and the drain unit 82 are both controlled by the controller 80.

By vertically moving the ring plate 37 with the Z-drive mechanism 85controlled by the controller 80, a distance H2 between a top surface ofthe air flow regulation ring 61 (or the substrate G mounted on the spinchuck 2D) and a bottom surface of the ring plate 37 can be controlled.In the present embodiment, the distance H2 was set as 25 mm. Thedistance H2 is preferably in a range from about 15 to 40 mm and morepreferably in a range from about 20 to 30 mm.

Under such arrangement of the cup 6 and the spin chuck 2D, when thesubstrate G is rotated at a low speed, a resist solution removed fromthe substrate G flows between the air flow regulation ring 61 and thering member 63 and a horizontally directed air flow is produced from thesurface of the substrate G and throughout the air flow regulation ring61. By producing the horizontally directed air flow at the spin chuck 2Din the present embodiment, despite a lack of a full understanding of themechanism thereof, a formation of turbulent air flow flowing through thetop surfaces of the comers of the substrate G is suppressed. Thus a highin-surface uniformity even throughout the periphery of the substrate Gcan be achieved as seen from examples to follow and, therefore, the sameeffects as in the above-mentioned cases are obtained. Further, whenperforming a high speed rotation process, since a resist solution flowedinto a gap between the substrate G and the air flow control members 26Dis discharged between the air flow control members 26D and the plate23D, a contamination of the substrate G or the plate 23D can beprevented and removability of the resist solution is improved, andthereby a desired film of solution with an appropriate thin film profilecan be obtained on the surface of the substrate G.

Further, in the present invention, the spin chuck 2D of this embodimentand the first cup 3 shown in FIG. 2 may be combined, and the spin chuck2 shown in FIG. 3A and the second cup 6 of the present embodiment may becombined.

In the present invention, the substrate G is not limited to the masksubstrate but may be, e.g., a glass substrate for a liquid crystaldisplay or a semiconductor wafer. Furthermore, the liquid processing ofthe present invention is not limited to a coating process of a coatingsolution process but may be applicable to other process such as adeveloping processing supplying a developing solution to an exposedsubstrate G and a cleaning process where a cleaning solution is suppliedto a substrate G.

Hereinafter, a coating and developing apparatus incorporating a liquidprocessing apparatus of the present invention as a coating unit U1 willbe described in detail with reference to FIGS. 15 and 16.

The reference numeral B1 represents a carrier block including a transfermechanism 72 and a carrier mount 71 having a carrier 70 foraccommodating a plurality of substrates G therein. A processing block B2is connected with an inner side of the carrier block B1. Installed abovethe blocks B1 and B2 is a fan filter unit (FFU) (not shown) from which aclean air is supplied downward, thereby producing a descending flow ofthe clean air in each of the blocks B1 and B2.

A transfer arm 5 is installed in the processing block B2. To surroundthe transfer arm 5, as viewed from the carrier block B1, the coatingunit (U1) and a developing unit (U2) for developing an exposed substrateare disposed on the right side of the transfer arm 5; a cleaning unit U3for wafer cleaning, on the left side of the transfer arm 5; and rackunits U4 and U5 each having a stack of heating/cooling units forproviding heating/cooling of the substrate and a receiving/fetching unitfor receiving and fetching the substrate, on the front and the rear sideof the transfer arm 5, respectively.

The transfer arm 5 is capable of moving along directions of X-axis,Y-axis and Z-axis, and θ-rotation about Z-axis. Such arrangement enablesthe transfer of a substrate G among the coating unit U1, the developingunit U2, the cleaning unit U3, and the rack units U4 and U5. Theprocessing block B2 is connected via an interface block B3 to anexposure block B4 for, e.g., exposing a substrate having a resist filmformed thereon by using a mask. A transfer mechanism 73 is installed inthe interface block B3 to enable a transfer of substrates G between areceiving/fetching unit (one of the racks in the rack unit U5) and theexposure block B4.

Flow of a substrate G in the apparatus will now be briefly described.First, the carrier 70 containing therein substrates G is carried intothe carrier mount 71 from outside. Then, a single substrate G isextracted from the carrier 70 by the transfer mechanism 72 and thesubstrate G is transferred to the transfer arm 5 by a receiving/fetchingunit (one of the racks in the rack unit U4). The substrate G is thenloaded into the cleaning unit U3, a heating unit, a cooling unit, andthe coating unit U1 in sequence to form, e.g., a resist layer, by theabove described process. Next, the substrate G is subjected to apre-baking in a heating unit, and is then cooled to a predeterminedtemperature in a cooling unit. Thereafter, the substrate G is loadedinto the exposure block B4 by the transfer mechanism 73 where thesubstrate G is exposed. The substrate G is then transferred to a heatingunit and a post-exposure baking process is performed thereon at apredetermined temperature. After adjusting a temperature of thesubstrate G in a cooling unit, the substrate G is developed in thedeveloping unit U2. Finally, the substrate G having, e.g., a resist maskpattern formed thereon by the above process is returned to the originalcarrier 70.

Experiments were performed in order to verify the effects of the presentinvention and the result will be described in detail hereinafter.

EXAMPLE 1

The present example employed the above-described method and theapparatus shown in FIG. 1 in forming a resist layer on a surface of amask substrate G. First, the substrate G was mounted on a spin chuck andthe resist solution film was formed in a high speed rotation process.The thinner contained in the resist solution was evaporated in a lowspeed rotation process to thereby obtain a resist layer.

A thickness of the resist layer formed on the surface of the substrate Gwas measured with a film thickness measuring device.

The process conditions were as follow:

-   -   (i) Dimensions of the substrate G: 152.4 mm×152.4 mm×6.35        mm(thickness)    -   (ii) Amount of coating solution supplied: 2 cc    -   (iii) High speed process: 2500 to 3200 rpm    -   (iv) Low speed process: 100 to 1000 rpm

EXAMPLE 2

The present example employed the apparatus shown in FIG. 14 and allother conditions were the same as in Example 1.

COMPARATIVE EXAMPLE 1

Comparative Example 1 employed a spin chuck disclosed in Japanese PatentLaid-open Publication No. 2000-271524 in coating a resist layer on amask substrate G. Other conditions remain the same as in Example 1.

Results of Example 1, Example 2 and Comparative Example 1

The thickness measurement result from Example 1 is illustrated in FIG.17. The thickness measurement result from Example 2 is illustrated inFIG. 18 and that from Comparative Example 1 is illustrated in FIG. 19.The vertical axis represents the thickness of the resist layer (nm). Itcan be seen that in Example 1 increment in the thickness of the resistlayer at corner portions of the substrate G is suppressed and a slantingof the thickness toward one direction at the side portions of thesubstrate G is suppressed as well. Also, in the results of Example 2, auniform thickness can be observed at the corner portions and the sideportions of the substrate G.

On the other hand, the resist layer obtained in the Comparative Example1 shows an increase in thickness at the corner portions thereof, as wellas a slant of the thickness at the side portions of the substrate G. Inother words, it was verified that a highly precise thickness profile canbe obtained by employing the spin chuck 2 not having the air flowcontrol members 26 at the regions corresponding to the corner portionsof the substrate G. Further, it was also verified that a highly precisethickness profile can be obtained by employing the air flow regulationring 61.

In accordance with the liquid processing apparatus of the presentinvention, by installing air flow control members around a substrateexcept regions corresponding to corner portions of the substrate, ahelical air flow including evaporative substance flowing from a centerportion to a periphery of the substrate along the surface thereof isproduced when the substrate is rotated. The helical air flowcontinuously flows through the top surfaces of the corner portions ofthe substrate. Accordingly, an increment in the film thickness at thecorner portions of the substrate is suppressed and, in terms ofthickness profile, high in-surface uniformity can be achieved. Moreover,by utilizing the corner portions of the substrate protruding in thecutout portions provided in the substrate supporting plate upon loadingand unloading of the substrate by, e.g., a transfer arm, the loading andunloading of the substrate can be easily performed. As a result, even ina case of, e.g., repeated processing of the substrate G, a deteriorationin throughput can be suppressed.

While the invention has been shown and described with respect to thepreferred embodiments, it will be understood by those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. A liquid processing method for forming a coating film on a polygonalsubstrate by spin coating in an ambient with a descending clean airflow, comprising the steps of: (a) supporting the polygonal substrate bya spin chuck and placing at least one air flow control member, whichrotates with the spin chuck, along a periphery portion of the substrateexcept at corner portions thereof; (b) supplying a top surface of thesubstrate supported on the spin chuck with coating solution andcentrifugally spreading the coating solution by rotating the spin chuckabout a normal axle; (c) removing a part of the coating solution on thetop surface of the substrate by rotating the substrate at a firstrotating speed; and (d) evaporating solvent included in the remainingcoating solution on the top surface of the substrate by rotating thesubstrate at a second rotating speed slower than the first rotatingspeed.
 2. The liquid processing method of claim 1, wherein in the step(a), a transfer arm is lowered relative to the spin chuck, and supportextrusions which support corner portions of the substrate are passedthrough cutout portions of the spin chuck when an area surrounded by thetransfer arm is passed through the spin chuck, whereby the substrate istransferred from the transfer arm to the spin chuck.
 3. A liquidprocessing method for forming a coating film on a polygonal substrate byspin coating in an ambient with a descending clean air flow, comprisingthe steps of: (a) supporting the polygonal substrate by a spin chuck andplacing at least one air flow control member, which rotates with thespin chuck, along a peripheral portion of the substrate except at cornerportions thereof; (b) supplying a top surface of the substrate supportedon the spin chuck with coating solution and centrifugally spreading thecoating solution by rotating the spin chuck about a normal axle; (c)removing a part of the coating solution on the top surface of thesubstrate by rotating the substrate at a first rotating speed, afterstopping the supplying of the coating solution is stopped; and (d)evaporating solvent included in the remaining coating solution on thetop surface of the substrate, by rotating the substrate at a secondrotating speed slower than the first rotating speed, wherein, at leastin the step (d), in addition to an air flow produced by the rotation ofthe spin chuck, a horizontally outward air flow is produced from aperiphery of the air flow control member.
 4. The liquid processingmethod of claim 3, wherein at the step (c), a coating solution removedfrom the substrate during a rotation thereof is drained through aportion below the air flow control member.